Make json_parser plugin handle case where Rack::Request#POST is calle…

…d previously for env on Rack 3 (Fixes #372)

The Rack 1-2 behavior did not cache rack.request.form_hash values
for data it didn't understand.  That changed in Rack 3, to fix
a bug in Rack that was open since 2014.  This updates the code
to work with all versions of Rack.  It now never checks
rack.request.form_hash or sets rack.request.form_input.

This approach is slightly slower for r.POST when given non-JSON
input, because it now checks the content_type when previously
it did not. Unfortunately, I don't see a way to avoid that.  I
did make the check faster by switching from a regexp to using
String#include?. In most cases, r.POST performance doesn't matter,
as users typically use r.params, and that is cached via an
instance variable, so r.POST is generally only called once per
request.

CHANGELOG

@@ -1,5 +1,7 @@
 === master
 
+* Make json_parser plugin handle case where Rack::Request#POST is called previously for env on Rack 3 (jeremyevans) (#372)
+
 * Fix strict_unused_block warnings when running specs on Ruby 3.4 (jeremyevans)
 
 = 3.87.0 (2024-12-17)

lib/roda/plugins/json_parser.rb

@@ -53,27 +53,28 @@ module RequestMethods
         # parse the request body as JSON.  Ignore an empty request body.
         def POST
           env = @env
-          if post_params = (env["roda.json_params"] || env["rack.request.form_hash"])
-            post_params
-          elsif (input = env["rack.input"]) && content_type =~ /json/
-            str = _read_json_input(input)
-            return super if str.empty?
-            begin
-              json_params = parse_json(str)
-            rescue
-              roda_class.opts[:json_parser_error_handler].call(self)
-            end
+          if post_params = env["roda.json_params"]
+            return post_params
+          end
+
+          unless (input = env["rack.input"]) && (content_type = self.content_type) && content_type.include?('json')
+            return super
+          end
+
+          str = _read_json_input(input)
+          return super if str.empty?
+          begin
+            json_params = parse_json(str)
+          rescue
+            roda_class.opts[:json_parser_error_handler].call(self)
+          end
 
-            wrap = roda_class.opts[:json_parser_wrap]
-            if wrap == :always || (wrap == :unless_hash && !json_params.is_a?(Hash))
-              json_params = {"_json"=>json_params}
-            end
-            env["roda.json_params"] = json_params
-            env["rack.request.form_input"] = input
-            json_params
-          else
-            super
+          wrap = roda_class.opts[:json_parser_wrap]
+          if wrap == :always || (wrap == :unless_hash && !json_params.is_a?(Hash))
+            json_params = {"_json"=>json_params}
           end
+          env["roda.json_params"] = json_params
+          json_params
         end
 
         private

spec/plugin/json_parser_spec.rb

@@ -11,6 +11,13 @@
     body('rack.input'=>rack_input('{"a":{"b":1}}'), 'CONTENT_TYPE'=>'text/json', 'REQUEST_METHOD'=>'POST').must_equal '1'
   end
 
+  it "Handles Rack::Request#POST being called in advance" do
+    env = req_env('rack.input'=>rack_input('{"a":{"b":1}}'), 'CONTENT_TYPE'=>'text/json', 'REQUEST_METHOD'=>'POST')
+    r = Rack::Request.new(env)
+    r.POST
+    body(env).must_equal '1'
+  end
+
   it "doesn't affect parsing of non-json content type" do
     body('rack.input'=>rack_input('a[b]=1'), 'REQUEST_METHOD'=>'POST').must_equal '1'
   end

spec/spec_helper.rb

@@ -170,8 +170,8 @@ def req(path='/', env={})
     _req(@app, env)
   end
 
-  def _req(app, env)
-    env = {"REQUEST_METHOD" => "GET", "PATH_INFO" => "/", "SCRIPT_NAME" => ""}.merge(env)
+  def req_env(env)
+    env = {"REQUEST_METHOD" => "GET", "PATH_INFO" => "/", "SCRIPT_NAME" => ""}.merge!(env)
     if ENV['LINT']
       env['SERVER_NAME'] ||= 'example.com'
       env['SERVER_PROTOCOL'] ||= env['HTTP_VERSION'] || 'HTTP/1.0'
@@ -187,7 +187,11 @@ def _req(app, env)
         env['rack.multiprocess'] = env['rack.multithread'] = env['rack.run_once'] = false
       end
     end
-    a = @app.call(env)
+    env
+  end
+
+  def _req(app, env)
+    a = @app.call(req_env(env))
 
     if ENV['LINT']
       orig = a[2]